Tuscaloosa formation (MSKt;0)

State	Mississippi
Name	Tuscaloosa formation
Geologic age	Upper Cretaceous
Original map label	Kt
Comments	Secondary unit descriptions from USGS Lexicon website (MS002), MS007, and MS009: All Cretaceous strata above the Paleozoic rocks and below the Eutaw Group are mapped and described in this report as the Tuscaloosa Group. Tuscaloosa that underlies Tishomingo Co. is primarily composed of chert gravel, sand, and clay lithologies equivalent to the western lithofacies as defined by Marcher and Stearns (1962). Exposures of the Gordo Formation equivalent gravels are limited to areas along the eastern county boundary south of U.S. Rte 72. Coker Formation does not occur in Tishomingo Co. The thickest of Tuscaloosa exposures in the study area occurs in a gravel pit 1.5 mi south of Rte 72. Here 20 ft of quartz-bearing gravels in a quartz sand matrix are overlain by 185 ft of sand, clay, and chert gravel. Group attains 418 ft in the subsurface of west-central Tishomingo Co. (Merrill and others, 1988). Gravels mapped as Tuscaloosa in Tishomingo Co., MS, southwestern TN, and northwestern AL are actually two distinct lithic units of different age. Lower gravels are chert gravel in a quartz sand matrix that can be traced southeast into the Gordo Formation. Upper chert gravel, with rare lenses of chert sand and kaolinitic clay unconformably overlies the lower unit and is best developed to the north in Tishomingo Co. This upper gravel is probably equivalent to the McShan Formation (Russell and Keady, 1990).
Primary rock type	sand
Secondary rock type	clay or mud
Other rock types	gravel
Lithologic constituents	Major Unconsolidated > Fine-detrital > Clay (Bed)Light and vari-colored irregularly bedded sand, clay, and gravel; gravel is mostly in lower portion. Unconsolidated > Coarse-detrital > Sand (Bed)Light and vari-colored irregularly bedded sand, clay, and gravel; gravel is mostly in lower portion. Minor Unconsolidated > Coarse-detrital > Gravel (Bed)Light and vari-colored irregularly bedded sand, clay, and gravel; gravel is mostly in lower portion.
Map references	Moore, William Halsell, 1969, reprinted 1985, Geologic Map of Mississippi, Compiled by Bicker, A. R., Jr., a revision of the geologic map published by the MS Geological Survey in 1945 in cooperation with the USGS, revised from data submitted by Dr. E. E. Russell of MS State University from published reports of the MS Geological Survey and from field revisions, Mercury Maps Inc., Jackson, MS.
Unit references	Moore, William Halsell, 1969, reprinted 1985, Geologic Map of Mississippi, Compiled by Bicker, A. R., Jr., a revision of the geologic map published by the MS Geological Survey in 1945 in cooperation with the USGS, revised from data submitted by Dr. E. E. Russell of MS State University from published reports of the MS Geological Survey and from field revisions, Mercury Maps Inc., Jackson, MS. USGS Geologic Names Lexicon (GEOLEX) [http://ngmdb.usgs.gov/Geolex/] Merrill, R.K., Gann, D.E. and Jennings, S.P., 1988, Tishomingo County geology and mineral resources [Mississippi]: Mississippi Office of Geology Bulletin, no. 127, 178 p. Russell, E.E. and Keady, D.M., 1990, Geologic mapping of Upper Cretaceous units in northeastern Mississippi, IN Bograd, M.B.E., and Dockery, D.T., III, eds., Geologic mapping in Mississippi; proceedings of the 1989 MISGEOMAP conference: Mississippi Office of Geology Circular, no. 3, p. 15-16.
Geographic coverage	Itawamba - Lowndes - Monroe - Tishomingo